Manga are just amazing as a collection thing. The volume covers are very pretty. If you can afford the 100 bucks go for it.
If you want something cheaper, you can gift him a couple of the smaller omnibus versions (3 volumes in 1):
Hate to be the boy-scout in the room but you could always just buy the omnibus on amazon. They sell them in three-volumes softcover books which comes up to a pretty decent price.
And now for the downvotes...